The match ball that Wayne Rooney took home to Manchester featured more than the signatures of his United team‑mates. "A few people were putting a few dodgy little messages on it," said the defender Chris Smalling, with a smile. "I saw Michael Owen writing something about Wayne's first touch on one of the goals but it was all jokes."

The United dressing room was a happy place to be at a little after 2.30pm on Saturday, with the manager, Sir Alex Ferguson, asserting that his team had "played like champions" in overturning a 2-0 deficit, thanks in large part to Rooney's hat‑trick.

It had been a classic United comeback; attacking substitutions made, no panic and a remorseless reeling in of their opponents, which culminated in decisive late goals.

When Rooney bent in his first from a free-kick around the poorly positioned defensive wall, it felt as if the die had been cast. West Ham United's capitulation, though, was worrying and total.

The mood in the United camp would be buoyed further. Arsenal's failure to beat Blackburn Rovers at home in the day's late kick-off had Ferguson and his players scenting a record 19th league title for the club. Moreover, they will travel to Chelsea on Wednesday for the first leg of their Champions League quarter-final believing that a repeat of the 1999 treble is a possibility.

"It was a message to Arsenal and Chelsea," said Ryan Giggs, who was moved to left-back for the second half against West Ham but played like an auxiliary left‑winger. "We've done it so many times ... we've ground out results, not played so well, although I thought we played really well here, even in the first half.

"The thing is that the bench looks strong. We've got players coming back. We've got Anderson; Nani's on the bench and he has been brilliant this season ... Dimitar Berbatov, Chico [Javier Hernández], Michael Owen. And they were the difference. Chico and Berbatov made the difference when they came on."

Rooney picked up the theme. "Our rivals would have known that this game wasn't over," he said. "A few years ago, when Chelsea won the league [under José Mourinho], they seemed to keep doing that. They would be losing [in an early kick-off] and then, when we had finished the warm-up, they had won the game. It is a bit of a blow but they [United's rivals] have to concentrate on their own job. The big games keep coming but you live for games like these. In some ways, we have to say our season starts now."

The never-say-die spirit has been ingrained by Ferguson and Smalling is the latest player to undergo the indoctrination. There remains an element of wide‑eyed wonder about the 21-year-old, who can scarcely believe what has happened to him.

When the new year broke in 2010, the former Maidstone United player had appeared in only two Premier League matches for Fulham. Now, after a £10m transfer to Old Trafford and injuries to key defensive personnel, most notably Rio Ferdinand, who has returned to training, Smalling is involved in matches that are watched by millions.

"To be a part of a comeback like that and to sign the ball for one of the biggest players is incredible but I really feel like I'm playing my part," he said. "Everybody just sticks together and they were all over the moon in the dressing room. It shows the emphasis on things here, how we don't give up and it's paid off. I'm starting to get a feel of the club's never-say-die attitude and I don't think many other teams possess that."

Smalling has bad memories of the Premier League fixture at Stamford Bridge on 1 March, when the referee Martin Atkinson adjudged him to have tripped Yuri Zhirkov for Frank Lampard's winning penalty. But Smalling suggested that he had seen nothing to fear about the London club.

"When we played at their place, they didn't create too many chances and in the first half, we dominated. It was unfortunate to get hard done by. We're going into Wednesday with a lot of confidence and so we should be. It's another massive stage for myself and to play in these games is what most players in the world would dream of."

West Ham felt that United's captain, Nemanja Vidic, ought to have been dismissed, if not immediately for the foul on Demba Ba after he had misjudged a high ball, then for a second yellow card in the 49th minute for a hack at the striker. United might have struggled at 2-0 down with 10 men. As it was, West Ham were worked all over the pitch and their energy levels appeared to hit a wall after the hour.

Ferguson remarked that the defeat had put West Ham "in real trouble". United have taken a bold stride forward.